Best mattress for me

Hi. I weigh 20 stone and am 5'8" tall. I suffer from a central nervous system problem and as soon as I lie down, I am in pain. My mattress has to be well padded as any mattress with springs in it becomes painful. I find 100% memory foam uncomfortable as when you lie on it, after a while, your body sinks into the mattress and it feels hard and uncomfortable if you lie in the same position for any length of time. I have considered buying a Hypnos pillow top mattress and wonder if that would be suitable for me. I must have something that feels soft but at the same time supportive. Can you advise a.s.a.p. Please.